Automatic telephone system



T. G. MARTIN.

"AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED DEC. I5, I9I6.

I Patented Apr. 27, 1920.

In Eula? srnrns PATENT onmon.

TALBOT G. MARTIN, OF CHICAGO, ILLINOIS ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Specification of Letters Patent.

7 Patented Apr. 27, 1920.

Application-filed December 15, 1916. Serial No. 137,153.

To all whom it may concern Be it known that I, TALBOT Gr. MARTIN, a citizen of the United States of America, and a resident of Chicago, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a specification. Y

My invention relates in general to auto matic telephone systems,and more particularly to automatic systems of the socalled two wire type in which the subscribers lines are provided with individual line switches In systems of the above general character, upon the removal of the receiver at a calling substation the line circuit is closed to operate the individual line switch associated therewith at the exchange, whereby connection is extended to the first of the numerical trunking switches to be used in establishing the connection. These numerical switches are responsive to momentary interruptions of the line circuit subsequently produced by he operation of a calling device with which the substation is provided.

In the commercial operation of such systems it happens quite frequently that a calling subscriber, in removing his receiver to initiate call, will accidentally manipulate his switch hook so as to send a preliminary impulse over the line circuit immediately after the line switch has operated and be fore he has operated his calling device. In other words, if the receiver is carelessly removed, the first closure of the line circuit may be followedby one or more interruptions before the receiver is completely disengaged from the hook. hen this occurs, it follows as a matter of course, that when the calling subscriber operates his calling device the first numerical switch will already have been operated and that a wrong number willtherefore be obtained.

The object of my invention is to obviate the difiiculty explained above by providing means for delaying the operation of the individual line switches. While the invention is applicable to various types of line switches including those of the rotary type, it is especially well suited for use with the well known master switch controlled plunger type of line switches, and such embodiment will be described hereinafter, refer once being had to the accompanying drawing. The figure of the drawing shows my invention diagrammatically.

In the drawing, the reference character A indicates a calling automatic substation whose line conductors 11 and 12 have been extended through the medium'of the individual line switch C to the trunk line terminating in the selector E. The line switch G, together with a number of similar line switches, is controlled in its trunk selecting operations by the master switch D. Inasmuch as all the apparatus shown is in general well known in the art, it will be described. but briefly, reference being had to prior patents hereinafter mentioned in lieu of a detailed description.

The substation A may be of any approved automatic type, such for example, as the substation shown in the British patent to Martin, No. 14.19 of 1910., As represented herein, it comprises essentially the receiver 2', transmitter 3, switch hook 4t, ringer 5, and condenser 6. Being an automatic substation, there is also provided a pair of impulse springs 7 and 8 controlled byan impulse wheel 9 through the medium of a finger hole dial (not shown).

The line conductors 11 and 12 of the substation A extend to the exchange where'they terminatein the individual line switch C, which is of the general type of line switch disclosed in the British patent to James, No. 26,301 of 1906; being, however, of the particular type shown in'U. S. Letters Patent No. 1,078,690, reissued April 13, 1915, as No. 13,901, to Frank Newforth. Through the medium of line switch 0 the line of substation A when calling is given access to a plurality of trunk lines each terminating in a numerical selector switch.

As previously mentioned, the line switch C and a plurality of other line switches are controlled in their trunk selecting operations by means of a master switch D. The master switch D is of the general type of master switch disclosed in the above mentioned British patent to James, No. 26,301 of 1906; being, however, more nearly of the particular type disclosed in U. S. Letters Patent No. 1,185,510, granted May 30, 1916, to A. Keith. As is well known, the function of the master switch is to maintain the plungers of all the idle line switches which it controls in position before the terminals of an idle trunk line.

One of the trunk linesto which the line switch C has access is indicated in the drawing by the reference characters 110, 120, and 130, and extends to the selector switch E, of which only the line and release relays are shown. The selector-'E'may be of the type shown in the above mentioned patent to q Newforth, No. 1,078,690.

While I have shown throughout the drawing a plurality of batteries, it is to be understood that there is preferably but one bat tery having its positive pole grounded, the

various battery leads ofthe drawing being connected together and extended to the negative pole thereof.

Having given a general description of the apparatus involved, I will now proceed 'to explain more in detail the operation of the same. In the following, the operation of the line switch C in extending connection responsive to the removal of the receiver at pull in winding 18 which may be traced over the following path: ground at G, armature 20 and its working contact, pullin winding 18, common conductor 21, windings and 24: of relay 22 in series, and contact sprmgs 2G to battery B. The winding 23 of relay 22 is of low resistance preferably not over 1 ohm, while the winding 24: should have at least 2500 ohms resistance. Consequently, upon the closure of the above Ollillli] the pull-in winding 18 is not operatively energized. The relay 22, however, is energized over the above circuit, although this operation is delayed somewhat by reason of a slug of copper with which its core is provided, and upon attracting its armature 25, short-circuits its high resistance winding 21, thereby permitting suflicient current to flow to operatively energize the pull-in winding 18. Upon energizing, the pull-in winding operates both the plunger arm 15 and the cut-off armature 16 the former through the medium of its plunger (not shown) forcing the bank springs 3033, inclusive, into engagement, respectively, with contacts 3 137, inclusive; and the latter disconnecting the line. conductors 11 and 12, respectively, from ground and the line relay 1 1.

By the engagement of' bank springs 30 and 33 with contacts 34'and 37, respectively,

the line conductors 11 and 12 are placed in" 3 connection, respectively, with the trunk conductors 110 and 120, which terminate in the .line relay 60 of the selector E. The line re lay 60 is accordingly energized over the loop circult including substation A and, upon attracting its armature,.closes a circuit for the slow-acting release'relay 61. Upon energizing in its turn, the release. relay closes switches having accessto the line of substation A where by a ground potential on these test contacts the said line is made busy. 7

In the foregoing, it has been assumed, of course, that immediately prior to the removal of the receiver the plunger of the line switch C and other idle plungers of the group were standing in front of'the terminal of the particular trunk line which is shown in the drawing and which extends to.

the selector E.

have been in engagement with the contact 7 This being the case, the 'Inaster switch wiper 10 would at that time 11, the locking arm 42 would have been rest- 7 ing in notch d3 of the locking plate 46, and

the arm 4A5 would have been in the proper position to close the contact springs Hth'the master switch n tlllS'POSltlOIl, as a result of the engagement of bank spring 32 with contact 36, a circuit for the starting relay 50 is completed by way of themaster switch wiper 10. Upon energizing, the starting relay 5O completes a circuit which includes the low resistance winding of the supervisory relay 53 and the windings of relays 51 and 52 in parallel. The locking relay 51, upon attracting its armature, disconnects the battery from relay'22 inorder; to prevent the operation of any'other line switches of the group while the master switch is moving their plungers toga new position, and at the same time disengages the locking arm 12 from the notch 43'. The relay 52, upon energizing, completes a holding circuit to maintain the starting relay.

50 energized after the wiper 40 has moved from contacts-1, and also completes .a circuit for the solenoid 55. J The solenoid-.55 nowdraws inits plunger, thereby rotating the plunger shaft 47 in clockwise direction un-l til the locking plate l6 and the wiper -10. reach the position shown in the drawing. 7 Although the circuit-of relay 52 isatonce broken as soon as the arm l i begins to move, its springs are retained in operated position by the detent 57 until the apparatus reaches the position shown, at which time the detent is disengaged by thearm 58 and the springs are allowed to separat The solenoid and the starting relay then doonc giro, followed by the deenergization of the relay 51; the latter operation permitting the locking of the shaft 4-? through the on .gement of the lo king arm 42 with the last notch in the locking plate 4:6. It is understood that by the rotation of the shaft a? as described, the plungers of all the idle line switches of the group are moved into positien before the terminals of the last or tenth trunk line, provided that such trunk line is not already busy. Subsequent calls will now operate the master switch under control of relays 50 and 51 to permit backward rotation of the plunger shaft 47 by the spring 59, whereby idle trunks may be successively selected in the usual and well known manner.

The foregoing operations have all taken place in response to the removal of the receiver substation A, lhe calling); subscriber may now proceed to operate his call ing device in accordance with the digits of the desirednumber, whereby the selector E and succeeding switches are actuated in the regular manner to complete the required connection. Since this latter operation is well understood and is in no way concerned with my invention the details thereof will be omitted.

It will be seen that my invention provides suitable means for delaying the energization of the operating: magnets of the individual line switches in a telephone system of th eneral character described, whereby accidental interruptions of the line circu t incident to the removal of the receivers at calling substations are prevented from having any ill effects on the successful operation of the system.

i hile I have shown and described. in the foregoing a certain particular embodiment of the invention, it is not to be limited to the precise form shown, but I desire on the contrary to include and have protected by Letters Patent all forms and modifications thereof which may come within the scope of the appended claims.

What I claim as my invention is:

1. In a telephone system, subscribers lines, trunk lines, an automatic switch for interconnecting a plurality of said lines,

means for initiating the operation of said switch, and means common to said subscribers lines for delaying the completion of the connection.

2. In a telephone system, subscribers lines, trunk lines, an automatic switch for interconnecting a plurality of said lines,

' said switch, and automatic means common to said subscribers lines for delaying the completion of the connection.

4-. In a telephone system, a subscribers line, a trunk line, an automatic switch for interconnecting said lines, an operating net for said switch, a circuit for said magnet, and a device in said circuit for preventing the immediate energization of said magnet when the circuit is closed.

In a telephone system, a subscribersline, a trunk line, an automatic switch for interconnecting; said lines, an operating mag net for said switch, a circuit for said magnet, subscriber controlled means for closing; said circuit, and a device in said circuit for delaying the effective energization of said mar;- net when its circuit is closed.

6. In a telephone system, a subsrribers line, a trunk line, an automatic switch for interconnecting said lines, an operating mag net for said switch, a circuit for said magnet including a high resistance relay, said ma n net being inoperative when the circuit is first closed, and means controlled by said relay for increasing; the flow of current through said magnet to operate the same. 7

7. In a telephone system, a subscribers line, a trunk line, an automatic switch individual to said line for extending connection to said trunk line, means controlled by the subscriber on said line for initiating the op eration of said switch, and automatic means common to a plurality of said subscribers lines for delaying; the completion of the connection.

8. In a telephone system, a subscribers line, a trunk line, an automatic switch individual to said line for extending connection to said trunk line, an operating mag net for said switch, a circuit for said magnet, means for closing said circuit, and means for preventing the immediate energization of said magnet after the circuit is closed.

9. In a telephone system, a subscribers line, a trunk line, an automatic switch individual to said line for extending connection to said trunk line, an operating magnet for said switch, a circuit for said magnet normally open at two points, a line relay energized upon the removal of the receiver to close said circuit at one point, and automatic means effective to close said circuit at the other point after a predetermined time.

10. In a telephone system, a subscribers line, a trunk line, an automatic switch individual to said line for extending connection to said trunk line, subscriber controlled means for initiating the operation of said switch, and automatic means'common to a plurality of said subscribers lines effective to introduce a definite time interval between the initial operation and'the final connecting operation of said switch. V

11. In a telephone system, a subscribers line, a trunk line, an automatic switch for 7 connecting said lines, subscriber controlled means for initiating theoperation of said switch when making a call, and automatic means common to a plurality of said sub lines, trunk lines, automatic switches for connecting said lines, a magnet for each switch for operating the same, a circuit for said magnet, means controlled irom'a subscribers line for closing said circuit, means for delaying the closure of said circuit, and automatic means for delaying the operation of said magnet after the closure of said circuit. 7

14. In a telephone system, subscribers lines, an automatic switch for connecting 1 said lines, a magnet for operating said switch,'a circuit for said magnet, means V controlled from a subscribers line for: closing said circuit, and automatic means for demagnet normally open at two points, a line relay energized upon the removal of the receiver to close said circuit at one point, automatic means effective to close said circuit at the other point after a predetermined time, and means for opening said circuit-at another 7 ated. V

16. In a telephone system, subscribers point when said magnet is operlines, trunk lines, automatic switches for connecting said lines, an operating magnet for each switch, a circuit for said magnet normally open at two points, a line relay energized upon the removal of the receiver to close said circuit at one point, automatic means common to a plurality of said subscribers lines efi'ective to close said circuit at the other point after a'predetermined time, and means when said magnet is operated for opening said circuit at another point to thereby prevent the operation of a second switch at the same time.

17. In a telephone system, a subscribers line, a trunk line, an automatic switch for connecting said lines, an operating magnet for'said switch, a circuit for said magnet including a high resistance relay, said mags net being inoperative when the circuit is first closed, and means controlled by said relay for short circuiting a portion of said resistance to thereby increase the flow of current through said magnet to operate the same.

Signed by me at Chicago, Cook county,

State of Illinois, this 11th day of December,

1916. I I I TALBOT G. MARTIN. 

